Research On Tunnel Anti-drainage And Cold-proof And Warm-proof Technology In High Altitude Environmental Sensitive Area

In recent years,more and more tunnels have been built in high-altitude cold regions,and the resulting freezing damage has received more and more attention.The problem of freezing damage has become one of the urgent problems to be solved in the construction of tunnels in high-altitude cold regions.At present,the main measures to solve this problem are to deal with the cold and warmth of the high-altitude cold zone tunnels,and if it is not handled or treated improperly,The tunnel drainage system will be ineffective due to freezing blockage,and the structure of the tunnel lining and pavement will be cracked and damaged due to frost heaving,and water seepage and icing will occur,which will pose a serious threat to the safety and operation of the tunnel.Therefore,it is of great practical significance to strengthen the cold-proof and warm-proof technology and water-proof and drainage technology of high-altitude cold zone tunnels.Based on the key scientific and technological project of Tibet Autonomous Region(2016XZ01G31),this paper takes the Mira Mountain Tunnel in Tibet as the research background,based on the theory of heat transfer and fuzzy mathematics,combined with on-site investigation,field test and numerical simulation to develop the cold-proof and warm-proof technology and water-proof and drainage technology of high-altitude cold zone tunnels.,the main research results are:(1)Research results of temperature field distribution law of Mira Mountain Tunnel:According to the project of the Mira Mountain Tunnel Project,the on-site temperature monitoring program was designed.From June 20,2017 to June 20,2018,the temperature changes in the tunnel inside and outside the tunnel and the temperature variation in the range of 0~5 m of the tunnel surrounding rock were monitored.It is concluded that the temperature change outside the hole is basically in accordance with the law of the cosine function.The temperature is highest in summer(June to August)and lowest in winter(January to February).As the tunnel depth increases,the temperature inside the tunnel gradually increases,and the heating rate gradually slows down.At the same time,the amplitude of the temperature in the cave changes with time as the tunnel depth increases.The surrounding rock temperature of the tunnel gradually increases with the increase of the radial depth of the tunnel,and the rate of change gradually decreases until the temperature tends to be constant.The maximum freezing depth of the surrounding rock of the portal section is 1.8 m.(2)Research results of the application of the active insulation system of the Mira Mountain Tunnel:The active insulation system is applied to the tunnel section of the Mira Mountain Tunnel.The differential equation of the thermal conduction of the tunnel surrounding rock under the action of the active insulation system is established by the principle of heat transfer.The set length and power of the active insulation system of the tunnel entrance are obtained by mathematical methods.The results show that in the Mira Mountain Tunnel,the laying range of the electric heating system is recommended to be from the tunnel entrance to the tunnel depth of 330m,and the operating power of the electric heating system in the range of 0-100 m is recommended to be 152 W/m~2,in the range of 100-200 m,the electric heating system power is recommended to be 131W/m~2,and the electric heating system power in the range of 200～330 m is recommended to be 107W/m~2.The numerical simulation of the surrounding rock temperature field of the tunnel portal section under the action of the active thermal insulation system is carried out to verify the correctness of the analytical calculation results.(3)Research results of the drainage and drainage system of the Mira Mountain Tunnel:According to the current domestic and international cold zone tunnel anti-drainage system,aiming at the climatic characteristics of the high-altitude cold zone,a set of anti-drainage schemes for deep-buried central ditch is proposed for the Mira Mountain Tunnel in Tibet.The specific plan is to start from the hole 0-500.The deep buried center ditch is set in the m range,and the depth of the central ditch at the entrance is the largest,which is 2.97 m.As the depth of the tunnel increases,the depth of the implant slowly becomes smaller until it reaches a depth of 500 meters.(4)Research results of evaluation methods for frost damage in high altitude cold regions:According to the on-site investigation and related data,the influences of the climatic conditions,hydrological conditions,geological conditions and artificial conditions of the tunnel area on the cold-proof and warm-proof and anti-drainage effects of the high-altitude cold zone tunnels are analyzed.Based on the fuzzy comprehensive evaluation theory.The comprehensive weighting method combining entropy weight method and improved analytic hierarchy process method establishes the evaluation model of tunnel freezing damage in high altitude cold region.Applying the model to the actual project of the Mira Mountain Tunnel,it is concluded that the temperature conditions,annual rainfall,tunnel depth and design problems have the greatest impact on the freeze damage results,and the temperature conditions play a decisive role.It can be seen that in the design of similar high-altitude cold zone tunnels,the temperature conditions of the tunneling area should be used as the main design basis to determine the freezing damage level of the tunnel.